Device for interrupting overloads



Jan. 11, 1944. F. KESSELRING 2,333,946

DEVICE FOR INTERRUPTING OVERLOADS Filed April 16, 1941 ATTOR/VEKS.

Patented Jan. 11, 1944 DEVICE FOR INTERARUPTING OVERLOADS.

Fritz Kesselring,

Berlin-Frohnau,

Germany vested in the Alien Property Custodian Application April 16, 1941, Serial No. 3883,753 In Germany September 28, 193.9,

Claims.

The present invention relates to an electric device for interrupting overload currents.

It is an object of the invention to provide a device for the interruption of overloads in which, during the interrupting operation, the intensity of the current is automatically and rapidly reduced to a low value, thereby facilitating and improving the-final interruption of the overload current.

According to the invention, a fuse, responsive to overloads to be interrupted, is combined with a resistance device to control the effective resistance in order to increase it value upon the occurrence of an overload. In one of its aspects the invention provides a resistance switching device (resistance switch) whose resistance is normally ineffective in the circuit to be controlled and becomes rapidly effective as soon a the switching device is released due to an overload. The rapid operation of such a resistance switch is fully utilized only if its release is effected with a correspondingly high rapidity. This is the reason why a fuse is employed according to the invention, since it is possible to attain with fuses much higher releasing speeds than with the customary tripping mechanisms. The combination of a resistance switch with a fuse releasing the same affords an effective suppression of overloads immediately upon their occurrence.

The fuse may be arranged in the form of a fusible cut-out. However, since it ha not the function of the ordinary fusible cut-outs but is relieved by the resistance of the resistance switch when interrupting the current, the fuse may be proportioned considerably smaller than the ordinary cut-outs. Above all, the fuse can be shorter than ordinarily, since the are occurring at the point of interruption is weakened by the immediately following insertion of a resistance into the circuit. As a result, the arc is rapidly extinguished or can be extinguished with the simplest auxiliary means. I An embodiment of the invention is shown in the accompanying drawing in diagrammatic form.

The leads u and 11 form part of the circuit to be interrupted. In this circuit, a resistance switch, comprising a resistance body w and a slide contact 8, is connected in series with the wire fuse a. The wire fuse is enclosed in an insulating tube or cylinder 1 and connected with the slide contact s through an electrically conductive connecting member 9. When in normal operating position, the contact 3 is pulled in the direction indicated by the arrow by a power storing device, for instance a spring 1. and is held in the position of rest against the action of the spring by the wire a. In this position, the effective resistance of the resistance device is negligible. When an overload occurs,.the wire a fuses and permits the spring f to move the contact s very rapidly towards the other end of the resistance body w. As a result, the resistance becomes effective with a rapidly increasing magnitude. Correspondingly, the current is immediately reduced to a considerable extent until the extinction of the are caused by the fusion of the Wire a effects the final interruption of th current. Tosupport the extinction of the are occurring at the Wire fuse, it is preferable to arrange in the neighborhood either gas-developing insulating materials or to surround the wire fuse with a pulverized insulating material, for instance quartz.

The vapors developed during the fusion of the wire a may also be utilized to accelerate the movable part of the resistance switch. To this end, a piston k, which is guided in the tube 1' in a sufficiently tight manner, is interposed between the Wire fuse a and the connecting member 9 designed in the form of a rigid rod. The piston la is forced by the gas pressure caused by the blowing of the fuse towards the open end of the tube, and thereby supports the driving force of the spring 1. The wire fuse is connected to the current supply conductor 12 through the conductive bottom b of the tube 1. The spring 1 is secured to the movable contact s by means of an insulating part i. Two insulating supports on which the tube 1' and the resistance body w are firmly mounted, respectively, are denoted by the reference character i. The spring f may be replaced by a power storing device of another type. for instance an energized electromagnet.

Devices according to the invention afford a safe interruption of currents of great intensity within the shortest time after the occurrence of an overload and without the formation of dangerous arcs.

What is claimed is:

1. Apparatus for interrupting an electric circuit in response to overloads, comprising resistance means connected with said circuit, control means for rapidly varying the effective resistance of said resistance means, and a fuse disposed in said circuit and connected with said control means for causing the latter to increase said effective resistance upon the blowing of the fuse in response to an overload.

2. Apparatus for interrupting an electric cir- 9 and cuit in response to overloads, comprising resistance means connected with said circuit, control means movable relative to said resistance means for varying the resistance effective in said circuit, power storing drive means connected with said control means and tending, when charged, to move said control means rapidly from an initial position of low resistance into a position of high resistance, and an overload-responsive fuse disposed in said circuit and mechanically associated with said drive means so as to hold said control means normally in said initial position and to release it upon the occurrence of an overload blowing the fuse.

3. Apparatus for interrupting an electric circuit in response to overloads, comprising a resistor connected with said circuit, a slide contact movable relative to said resistor for varying the effective resistance, power storing drive means for moving said slide contact from an initial position of low resistance into a position of high resistance, and an overload-responsive fuse'disposed in said circuit and mechanically associated with said drive means for releasing said drive means in response to an overload so as to control said slide contact to rapidly increase said effective resistance upon the blowing of the fuse.

4 Apparatus for interrupting an electric circuit in response to overloads, comprising resistanCe means connected in said circuit, a slide contact movable relative to said resistance means for varying the effective resistance value, power storing drive means connected with said slide contact for moving, when charged, said slide contact from an initial position of substantially ineifective resistance into a position of high resistance, and releasable locking means for holding said spring in tensioned condition, said lockin means including a fuse connected in said circuit in series with said resistance means for releasing said drive means upon the occurrence of an overload blowing the fuse, whereby the increasing efiective resistance causes the extinction of the are occurring at the blowing fuse.

5. Apparatus for interrupting an electric circuit in response to overloads, comprising resistance means connected with said circuit, control means movable relative to said resistance means for-varying the resistance effective in said circuit, power storing drive means connected. with said control means and tending, when charged, to move said control means rapidly from an initial position of ineffective resistance into a position of high resistance, in combination with two ter- .minals movable relative to each other, one of said terminals being connected with said control means, and a fuse connected between said terminals to prevent normally said control means from following the tendency of said drive means and for releasing, when blowing due to an overload, said drive means together with said control means and the terminal connected with the latter, whereby said effective resistance is rapidly increased and said terminals are simultaneously moved away from each other to coact in extinguishing the are occurring at the fuse.

FRITZ KESSELRING. 

